Heater temp knob adjustment?

[Das Delfin]

The cliff notes would be this paragraph

"Basically, the E30 uses a heater valve bolted directly to the heater matrix under the dash which gives very fast response to the heater control. It’s a simple valve which sits between the heater matrix and the engine and with the application of a full 12 volts, closes the solenoid valve and thus shuts off the warm water supply and therefore the heat.
The temperature switch on the dash is a rheostat which alters the voltage going to this valve. When set to cold, there’s a full 12 volts on the valve, when set half-way about 6 volts mean- ing a half-open valve and when set to full heat, no volts at all."

and this sentence

"The switch on the E30 operates both the heater valve and the hot air flap in the heater box via a cable."

so that plus the hot air flap which controls direction of air (flow to the hand vents) and use realoem to find diagrams of the vent ducting and note that they flow from different parts of the heater box = fuckin complicated ass german shit

[Das Delfin]

Honestly I learned a lot from this thread. I didn't know that:

- the car's heater control valve was electronic (though it makes sense because cars are supposed to have a valve which shuts off or regulates hot water flow to the heater core, rather than a flap which has almost zero insulation properties whatsoever)

- this means the electronic valve can break

- the car adjusts heat from the defrost and floor accordingly

- the hand vents aren't really outside temp but are a mix of outside and what is going to the floor according to the temp knob

- there might be a temp sensor (though I haven't read as much on that other than what is in the owners manual and on a realoem diagram)

- the cold-air-on-face feature is really cool! I thought this was only on the e36

- I thought the heater control valve was only 100% open at full cold and 100% open on anything other than full cold. Contrary to what I thought, it varies in temp (which if you google pics of the temp selector you will see electronics that are part of it which do exactly what is listed in that article. Also if you realoem search the part number, google it, and find the price of a brand new one you notice it's like $700 which implies there are electronics involved).

- it makes sense why there is a control for each hand vent as well as all the hand vents together. You want to be able to turn off the cool air from every which way if it's bothering you

- the heater control valve isn't hard to replace (same with the heater core)

- since starting researching for this thread I've been more acquainted with my car's hvac and I don't get frustrated with boiling hot heat anymore. I just turn off the hand vents!

[imjusthere]

I too would like to thank everyone for the excellent information. I'm pleased to know there isn't anything wrong with my HVAC and am much happier now that I have a better understanding of how my heating system works. My life will be much more comfortable for it.

Sent from my XT1254 using Tapatalk

[Dave_G]

Honestly I learned a lot from this thread.

Yeah, I think a lot of us did. I know I did.

Also if you realoem search the part number, google it, and find the price of a brand new one you notice it's like $700 which implies there are electronics involved).

It's actually around $200. When I bought one five years ago (which I ended up not needing) I paid $135. Prices for E30 parts are rising. But at least we can still get them, which you can't say about a lot of 25-30 year old cars.

[Das Delfin]

^ from what I briefly saw on ecs and pelican it was 700 ish. Thought I don't doubt the price change. I bought a behr blower motor a couple years ago and went to recommend it to a friend last year only to find out it had been discontinued :O